In bank-note processing apparatus bank notes are checked with the aid of sensors for example for their denomination, currency, authenticity or for their state. For this purpose the bank notes are conveyed by a transport system and in doing so pass a sensor path with one or more sensors. In doing so, the bank notes are transported substantially parallel to the surface of the sensor facing the bank notes. The sensor surface is usually a plane surface having merely a small number of gaps, e.g. for measuring heads or windows, but without any elevated or depressed areas. In some sensors, the bank notes transported past slide on the sensor surface at least temporarily. However, through the sliding along of the bank notes the sensor surface is soiled and worn in the course of time. What is more, contact with the bank notes takes place randomly and in an undefined fashion, leading to an unsteady transport, e.g. the fluttering of the bank notes. This has an adverse effect on the reproducibility of the measuring results. In order to minimize the friction between the bank note and the sensor surface the sensor surface is consequently designed so as to be as flat as possible. A further disadvantage of contact-type transport is the electrostatic charge of the bank note due to the friction between the bank note and the sensor surface. For these reasons obstructions occur again and again in bank note transport when bank notes are transported past the known sensors.